The effects of electron-acceptor strength on the electronic properties of thieno[3,2-b]thiophene-based donor–acceptor copolymers

Abstract:

The donor-acceptor(D-A) conjugated copolymer were designed by choosing Thieno[3,2-b]thiophene(TT) as the electron donor and quinoxaline(Q), Benzo[c][1,2,5]thiadiazole(BT), pyrazino[2,3-g]quinoxaline(PQ), [1,2,5]thiadiazolo[3,4-g]quinoxaline (TQ) or Benzobis[1,2,5]thiadiazole (BBT) as the electron acceptor unit. The DFT/B3LYP method is employed to investigate the electronic structures and properties of the donor-acceptor alternating copolymers. The theoretical results suggest that electron-acceptor strength contribute significantly to the geometrical structures and electronic properties of the alternating donor-acceptor copolymers. The geometrical and electronic properties of the TT-based copolymers exhibit a systematic trend with the electron-acceptor strength within a certain range. The bond length alternation, band gap (Eg) and hole effective mass decrease, the bandwidth (both valence and conduction band) increases systematically with an increase in the electron-withdrawing ability of the acceptor moiety within a certain range of the electron-acceptor strength.